The mucosal immune system is now recognized as a major, functionally-distinct branch of the immune system that plays a pivotal role in defense of mucosal surfaces. Recently there has been a surge of interest in developing novel strategies for targeting vaccines to mucosal inductive sites. A limiting factor in the development of such vaccines is our incomplete understanding of the cellular and molecular interactions of antigens, pathogens and vaccines with cells of mucosal tissues. Novel current research is addressing the complex interplay of antigens, epithelial cells, and local mucosal lymphocytes and antigen presenting cells, and new insights into these events are now emerging. A Keystone Conference entitled "MUCOSAL IMMUNITY: CELLULAR AND MOLECULAR CROSS-TALK AT MUCOSAL SURFACES" will be held in March 1997 at Santa Fe, New Mexico. The proposed meeting will bring together scientists from diverse fields including cellular and molecular immunology, epithelial cell biology, microbia pathogenesis and vaccinology, to focus on the sampling of foreign antigens and pathogens across epithelial barriers, and the cellular and molecular cross-talk at mucosal surfaces that leads to protective immune responses. Resent meetings related to mucosal immunity and vaccines held over the past 2 years have been very broad in scope. In contrast, the proposed Keystone Conference will focus specifically on the cellular and molecular events at epithelial surfaces that underlie mucosal immune responses. Because of this emphasis on basic science, it is particularly important to include young scientists in training from diverse disciplines who will be the future innovators in this rapidly-changing field.